Engine systems may utilize recirculation of exhaust gas from an engine exhaust system to an engine intake system, a process referred to as exhaust gas recirculation (EGR), to reduce regulated emissions. Turbocharged engines may include a low-pressure EGR (LP EGR) system, a high-pressure EGR (HP EGR) system, or both. The LP EGR system diverts exhaust gases after the gases pass through the turbine of the turbocharger and injects the gases before the compressor, while the HP EGR system diverts exhaust gases before the turbine and injects the gases after the intake throttle. An EGR valve may be controlled in either example to achieve a desired intake air dilution, the desired intake air dilution based on engine operating conditions to maintain desirable combustion stability of the engine while providing emissions and fuel economy benefits.
However, the inventors herein have recognized issues with the above approaches. An engine system including only a LP EGR system has a long transport delay, as the exhaust gases must travel through the turbocharger compressor, high pressure air induction plumbing, charge air cooler, and intake manifold before reaching the combustion chamber. As a result, it may be difficult to provide the desired amount of EGR to the cylinders, particularly during transient conditions. This is due to the fact that, by the time the EGR reaches the cylinder, the engine speed/load state may have changed and another EGR rate may be desired. An engine system including only a HP EGR system has a reduced EGR delivery time, but the percentage of EGR gases compared to intake gases may be limited and the ability to provide sustained EGR delivery may be compromised by low exhaust pressures. An engine system including a both a LP EGR system and a HP EGR system may experience energy losses due to increased cooling requirements of hot exhaust gases and an increased complexity of valve arrangement. Additionally, the ability to supply secondary air injection to the exhaust system may be controlled by an additional system separate from the LP and EGR systems, further increasing the complexity of the engine system arrangement.
In one example, the issues described above may be addressed by a method for adjusting a flow of coolant through a gas mixing tank reservoir fluidly coupled to each of an intake system and exhaust system of an engine in response to a request to supply one or more of secondary air injection to the exhaust system and exhaust gas recirculation to the intake system via the reservoir, based on a temperature of the coolant entering the reservoir. In one example, the exhaust gas recirculation (EGR) may include both low pressure (LP) EGR and high pressure (HP) EGR. In this way, LP EGR, HP EGR, and secondary air injection may be provided to the engine system through the use of a shared gas mixing tank reservoir. The flow of coolant to the gas mixing tank reservoir may be controlled in order to adjust the temperature of the contents of the gas mixing tank reservoir according to engine operating conditions. Additionally, the ratio of compressed air from the intake manifold and exhaust gas from the exhaust manifold may be controlled within the gas mixing tank reservoir to fulfill one or more particular applications based on engine operating conditions (e.g., LP EGR, HP EGR, and/or secondary air injection). By controlling the temperature of the gases and the ratio of the gases within the gas mixing tank reservoir, the gas mixing tank reservoir can be utilized with a wide variety of engine operating conditions to increase engine performance and lower emissions.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.